#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;

#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a) - 1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define sz(x) (int)(x).size()
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define ins insert

const char nl = '\n';

int bst[42][42][810];

int N, K;
string S;
set<array<int, 4>> vis;

void go(int p, int n, int na, int nac) {
    if (p == N) {
        if (nac != K) return;
        cout << S << nl;
        exit(0);
    }
    if (nac > K || nac + bst[N-p][n][na] < K || (nac < K && nac + na > K)) return;
    if (vis.find({p,n,na,nac}) != vis.end()) return;
    vis.ins({p,n,na,nac});
    char old = S[p];
    if (S[p] == '?' || S[p] == 'N') {
        S[p] = 'N';
        go(p+1, n+1, na, nac);
        S[p] = old;
    }
    if (S[p] == '?' || S[p] == 'A') {
        S[p] = 'A';
        go(p+1, n, na+n, nac);
        S[p] = old;
    }
    if (S[p] == '?' || S[p] == 'C') {
        S[p] = 'C';
        go(p+1, n, na, nac+na);
        S[p] = old;
    }

    if (S[p] != 'N' && S[p] != 'A' && S[p] != 'C') {
        if (S[p] == '?') S[p] = 'X';
        go(p+1, n, na, nac);
        S[p] = old;
    }
    
}

void solve() {
    cin >> N >> K;
    cin >> S;
    F0R(rem, 42) {
        F0R(n, 42) {
            F0R(na, 810) {
                F0Rd(c, rem+1) {
                    F0Rd(a, rem-c+1) {
                        int nn = rem-c-a;
                        bst[rem][n][na] = max(bst[rem][n][na], (na+(n+nn)*a)*c);
                        if (bst[rem][n][na] >= K) goto done;
                    }
                }
                done:
                ;
            }
        }
    }

    go(0,0,0,0);
    cout << -1 << nl;

}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	solve();
	return 0;
}